Dual-AAV vector-mediated expression of MYO7A improves vestibular function in a mouse model of Usher syndrome 1B

Samantha C Lau; Mhamed Grati; Kevin Isgrig; Moaz Sinan; Kaitlyn R Calabro; Jianliang Zhu; Yasuko Ishibashi; Zeynep Ozgur; Talah Wafa; Inna A Belyantseva; Tracy Fitzgerald; Thomas B Friedman; Sanford L Boye; Shannon E Boye; Wade W Chien

doi:10.1016/j.omtm.2023.08.012

Dual-AAV vector-mediated expression of MYO7A improves vestibular function in a mouse model of Usher syndrome 1B

Mol Ther Methods Clin Dev. 2023 Aug 21:30:534-545. doi: 10.1016/j.omtm.2023.08.012. eCollection 2023 Sep 14.

Authors

Samantha C Lau¹, Mhamed Grati¹, Kevin Isgrig¹, Moaz Sinan¹, Kaitlyn R Calabro², Jianliang Zhu¹, Yasuko Ishibashi^{1

3}, Zeynep Ozgur¹, Talah Wafa⁴, Inna A Belyantseva³, Tracy Fitzgerald⁴, Thomas B Friedman³, Sanford L Boye⁵, Shannon E Boye², Wade W Chien^{1

6}

Affiliations

¹ Inner Ear Gene Therapy Program, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA.
² Division of Cellular and Molecular Therapy, Department of Pediatrics, University of Florida, Gainesville, FL, USA.
³ Laboratory of Molecular Genetics, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA.
⁴ Mouse Auditory Testing Core Facility, National Institute on Deafness and Other Communication Disorders, National Institutes of Health, Bethesda, MD 20892, USA.
⁵ Powell Gene Therapy Center, Department of Pediatrics, University of Florida, Gainesville, FL, USA.
⁶ Department of Otolaryngology - Head & Neck Surgery, Johns Hopkins School of Medicine, Baltimore, MD, USA.

Abstract

Usher syndrome is the most common cause of deafness-blindness in the world. Usher syndrome type 1B (USH1B) is associated with mutations in MYO7A. Patients with USH1B experience deafness, blindness, and vestibular dysfunction. In this study, we applied adeno-associated virus (AAV)-mediated gene therapy to the shaker-1 (Myo7a^{4626SB/4626SB}) mouse, a model of USH1B. The shaker-1 mouse has a nonsense mutation in Myo7a, is profoundly deaf throughout life, and has significant vestibular dysfunction. Because of the ∼6.7-kb size of the MYO7A cDNA, a dual-AAV approach was used for gene delivery, which involves splitting human MYO7A cDNA into 5' and 3' halves and cloning them into two separate AAV8(Y733F) vectors. When MYO7A cDNA was delivered to shaker-1 inner ears using the dual-AAV approach, cochlear hair cell survival was improved. However, stereocilium organization and auditory function were not improved. In contrast, in the vestibular system, dual-AAV-mediated MYO7A delivery significantly rescued hair cell stereocilium morphology and improved vestibular function, as reflected in a reduction of circling behavior and improved vestibular sensory-evoked potential (VsEP) thresholds. Our data indicate that dual-AAV-mediated MYO7A expression improves vestibular function in shaker-1 mice and supports further development of this approach for the treatment of disabling dizziness from vestibular dysfunction in USH1B patients.

Keywords: AAV; MYO7A; USH1B; Usher syndrome; dual-AAV; gene therapy; hearing loss; vestibular dysfunction.